PSG have been criticised for leaving Kylian Mbappe out of their preseason tour.
Mbappe, who has been transfer-listed by PSG, has less than a year to run on his contract after refusing to take up a 12 month option in his contract.
And PSG have decided against taking him on tour - and decision which is being threatened by legal action by the National Union of Professional Footballers.
The union statement said: "These players must enjoy the same working conditions as the rest of the professional workforce.
"The UNFP feels it would be useful to remind managers that putting pressure on an employee - via the deterioration of their working conditions, for example - to force them to leave or accept what the employer wants constitutes moral harassment, which French law firmly condemns.
"The UNFP reserves the right to take civil and criminal action against any club that behaves in this way."
